JPH02304868A - Alkaline battery and its negative active material - Google Patents

Abstract

PURPOSE:To reduce hydrogen gas evolution in the low content of mercury by using amalgamated zinc alloy powder containing a specified amount of each of bismuth, lead, aluminium, indium, and mercury. CONSTITUTION:A negative active material comprising zinc alloy powder containing 0.01-0.5wt.% bismuth, 0.005-0.5wt.% lead, 0.001-0.005wt.% aluminium, 0.005-0.2wt.% indium, and 0.001-1.0wt.% mercury is used. The content of mercury is required to reduce to 1.0wt.% or less as social needs. By synergistic effect of these elements added, hydrogen gas evolution is further reduced compared with conventional low mercury amalgamated zinc alloy powder, and furthermore discharge performance is increased.

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to an alkaline battery and its negative electrode active material, and more specifically, it is made of a zinc chloride alloy powder containing bismuth, lead, aluminum, indium, and mercury within a specific range. ,
A negative electrode active material that reduces the amount of gas generated even at low mercury levels, does not cause abnormal gas generation or abnormal discharge, and maintains discharge characteristics, which are battery performance, at a high level, and an alkaline battery using the negative electrode active material. .

[Prior Art] In an alkaline battery using zinc as a negative electrode active material, a strong alkaline electrolyte such as an aqueous potassium hydroxide solution is used, so the battery must be sealed tightly. This sealing of the battery is particularly important when attempting to miniaturize the battery, but it also traps hydrogen gas generated due to corrosion of zinc during battery storage. Therefore, during long-term storage, the gas pressure inside the battery increases, and the more completely the battery is sealed, the greater the risk of explosion.

As a countermeasure, research has been conducted to prevent the corrosion of zinc, which is an active material for the negative electrode, and to reduce the generation of hydrogen gas inside the battery.The use of zinc chloride powder, which utilizes the hydrogen overvoltage of mercury, as an active material for the negative electrode has been studied. It is carried out exclusively. For this reason, the negative electrode active materials of alkaline batteries commercially available today are 1.
5-1 (about 1% by weight), and as a social need, there are strong expectations for the development of lower mercury or mercury-free batteries.

Therefore, various proposals have been made regarding zinc alloy powders in which various metals are added to zinc in order to reduce the mercury content in batteries. For example, zinc alloy powder made by adding lead to zinc,
Alternatively, there is a zinc alloy powder made by the inventors of the present invention in which lead and aluminum are added to zinc.

Among these, zinc alloy powder containing aluminum is attracting attention and being used because it has a great effect of suppressing gas generation and is an effective material for reducing stress.

[Problems to be Solved by the Invention] However, when aluminum-containing zinc alloy powder is used as a negative electrode active material, there is a problem in that the discharge performance rapidly deteriorates particularly during light load discharge.

As a result of disassembling and examining the internal parts of these batteries with degraded discharge performance, it was found that internal short circuits were caused by discharge reaction products.

The reason why this phenomenon occurs is thought to be as follows.

That is, the zinc alloy powder containing aluminum or a specific crystal grows when discharged with a specific current, and this crystal penetrates the separator, resulting in a short circuit phenomenon.

In view of the above circumstances, the present invention suppresses the generation of hydrogen gas from the zinc oxide alloy powder used as the negative electrode active material even with a low amount of mercury, maintains the discharge performance at a high level, and maintains the discharge performance after partial discharge. It is an object of the present invention to provide an alkaline battery that generates less gas and does not cause abnormal discharge such as internal short circuit, and its negative electrode active material.

[Means and effects for solving the problem] In order to achieve the above object, the present inventors conducted intensive research, and found that bismuth, lead, aluminum, indium, and mercury were all added in a specific range, and this was added to the anode active material. It was discovered that when used in materials, due to the synergistic effect of these additive elements, the amount of hydrogen gas generated was further reduced than with conventional low-rate zinc alloy powders, and an alkaline battery with excellent discharge performance could be obtained. We have arrived at the present invention.

That is, in the present invention, bismuth is 0.01 to 0.5% by weight, lead is 0.005 to 0.5% by weight, and aluminum is 0.01 to 0.5% by weight.
．． 001-0.005% by weight, 0.005% indium
-0.2% by weight and 0.001 to 1.0 parts by weight of mercury, and an alkaline battery using the negative electrode active material.

The present invention will be explained in more detail below.

In the present invention, the zinc oxide alloy powder used as the negative electrode active material contains 0.005 to 0.5% by weight of lead (50 to 5000 ppn+ by weight) and 0.00% by weight of bismuth, as described above. O
1-0.5% by weight (100-5000% by weight IIpII+
), aluminum 0.001-0.005% by weight (1
0-50 ppI by weight, indium 0.001-0.
2% by weight (10 to 2000 weight pIllff), 0.001 to 1.0% by weight of mercury, and the balance consists of zinc.

When the content of lead, bismuth, aluminum, and indium is less than the above lower limit, the effect of the content on suppressing hydrogen gas generation and improving discharge performance when the negative electrode active material is placed in an alkaline battery is small, and when the content exceeds the upper limit. Even if it is added, no further effect will be produced. Additionally, the mercury content must be kept at 1.0% by weight or less to meet social needs.

The zinc chloride alloy powder used as the negative electrode active material is
Strictly control the raw materials and manufacturing process to keep accompanying impurities iron below 20 ppm by weight, chromium below 5 ppm by weight, and molybdenum, arsenic, vanadium, antimony, and germanium below 1 ppra by weight each. is desirable.

Although the method for producing such a zinc chloride alloy powder is arbitrary, the following three methods are exemplified.

(1) Add a predetermined amount of additional elements lead, bismuth, aluminum, or indium in addition to these into molten zinc, stir and alloy, then atomize with compressed air, turn into powder, and sieve. The granulated zinc alloy powder is subjected to wet or dry amalgamation using mercury-indium amalgam to obtain an aqueous zinc alloy powder.

<2> Add a predetermined amount of additional elements lead, bismuth, aluminum, and indium to the molten zinc, stir to alloy, and then atomize with compressed air and turn it into powder.
The sieved and sized zinc alloy powder is subjected to wet or dry sieving with mercury to obtain a sieved zinc alloy powder.

(3) Predetermined amounts of additive elements lead, bismuth, aluminum, indium, and mercury are added to molten zinc, stirred to form an alloy, and then atomized with compressed air, pulverized, and sieved. The hydrated zinc alloy powder is obtained by sizing the powder (melting process).

The wet process referred to here means that the zinc alloy powder obtained by pulverization and mercury or mercury-indium amalgam are put into, for example, a 1096 potassium hydroxide aqueous solution, mixed and stirred to perform the process of forming a liquid. A zinc chloride alloy powder is obtained. In addition, dry oxidation involves putting the zinc alloy powder obtained by pulverization and mercury or mercury-indium amalgam into a mixer such as a ribbon blender, and mixing and stirring in a constant atmosphere for about 5 to 20 minutes. At the same time, carry out the filtration process,
A zinc chloride alloy powder is obtained.

By using the zinc oxide alloy powder obtained in this way as a negative electrode active material, it is possible to obtain an alkaline battery that not only suppresses hydrogen gas generation before discharge or after partial discharge, but also shows no abnormal discharge. .

The alkaline battery of the present invention uses an alkaline aqueous solution containing caustic potash, caustic soda, etc. as the main components as an electrolyte, uses the above-mentioned zinc chloride alloy powder as a negative electrode active material, and uses manganese dioxide, silver oxide, oxygen, etc. as a positive electrode active material. It can be obtained by

EXAMPLES] Hereinafter, the present invention will be specifically explained based on Examples. The content ratio of each element in Table 1 is the content ratio in the finally obtained zinc chloride alloy powder, and the unit is based on weight.

Examples 1 to 14 and Comparative Examples 1 to 4 Zinc alloy powders having the compositions shown in Table 1 were prepared by the following five methods.

(1) Adding specified amounts of additive elements listed in Table 1 to molten zinc,
After stirring and alloying, the mixture was atomized with compressed air, pulverized, sieved, and sized to obtain zinc alloy powder (atomized powder).

Next, this zinc alloy powder and mercury-indium amalgam were dry blended using a ribbon blender to obtain zinc alloy powders having the compositions shown in Table 1 (Examples 1 to 11).

(2) Adding specified amounts of additive elements listed in Table 1 to molten zinc,
After stirring and alloying, the mixture was atomized with compressed air, pulverized, sieved, and sized to obtain zinc alloy powder (atomized powder).

Next, this zinc alloy powder and mercury were dry-blended using a ribbon blender to obtain a blister-zinc alloy powder having the composition shown in Table 1 (Example 12).

(3) Adding specified amounts of additive elements listed in Table 1 to molten zinc,
After stirring and alloying, it was atomized with compressed air, pulverized, sieved and sized to obtain zinc hydrate alloy powder (atomized powder) having the composition shown in Table 1.
Example 13).

(4) Adding specified amounts of additive elements listed in Table 1 to molten zinc,
After stirring and alloying, the mixture was atomized with compressed air, pulverized, sieved and sized to obtain a zinc alloy powder (atomized powder). Next, this zinc alloy powder was put into a 10% potassium hydroxide aqueous solution, immersed in mercury with stirring to perform a filtration treatment, washed with water, filtered,
Drying was performed to obtain zinc chloride alloy powders having the compositions shown in Table 1 (Example 14 and Comparative Example 4).

(5) Adding specified amounts of additive elements listed in Table 1 to molten zinc,
After stirring and alloying, the mixture was atomized with compressed air, pulverized, sieved and sized to obtain a zinc alloy powder (atomized powder). Next, this zinc alloy powder was put into a 10% potassium hydroxide aqueous solution, and the mercury-
Indium amalgam was soaked under stirring, subjected to a filtration treatment, washed with water, filtered and dried to obtain zinc hydrate alloy powders having the compositions shown in Table 1 (Comparative Examples 1 to 3).

The thus obtained zinc hydrate alloy powder is used as a negative electrode active material, and is gelled using this negative electrode active material, a gelling agent, and an electrolytic solution in which 40% potassium hydroxide solution is saturated with zinc oxide. was used as a negative electrode material, and a positive electrode material was prepared by mixing manganese dioxide and a conductive agent with the positive electrode. Using these negative electrode materials and positive electrode materials, a test was conducted using an alkaline manganese battery having a configuration similar to that of a commercially available battery (LR-8) shown in FIG.

The alkaline manganese battery shown in Figure 1 consists of a positive electrode can 1, a positive electrode 2,
Negative electrode (gelled zinc alloy powder) 3, separator 4, sealing body 5, negative electrode bottom plate 6, negative electrode current collector 7, cap 8, heat-shrinkable resin tube 9, insulating rings 10, 11
, an exterior can and a positive electrode can 12.

This battery was assembled into 10 batteries each using different types of zinc chloride alloy powder used for the negative electrode, and stored at 60°C for 20 days.The amount of hydrogen gas generated per battery at that time was
were measured, and the average value of each 10 measurement results is shown in Table 1.

Gas generation after partial discharge is determined by discharging for 1/2 of the discharge time when discharging with a resistance of 1 Ω, then storing it at 60°C for 20 days in the same manner as above, and reducing the amount of hydrogen gas per battery at that time. The amount generated (rd) was measured, and the average value of the 10 measurement results is shown in Table 1.

In addition, for each battery, a continuous discharge test was conducted with 10 batteries each under a 2Ω load, and the average value of the discharge time was determined in Comparative Example 4.
The value is expressed as an index with the value as 100.

Furthermore, regarding abnormal discharge, for example, when continuously discharging under a light load of 300Ω, if a rapid voltage drop occurs,
, Those that do not cause a rapid voltage drop are indicated as O in Table 1.

These results are shown in Table 1 together with the composition of the zinc chloride alloy powder used as the negative electrode active material.

As shown in Table 1, in Examples 1 to 14, regardless of the manufacturing method of the zinc chloride alloy powder used as the negative electrode active material,
It is clear that the abnormal gas generation after 1/2 discharge shown in Comparative Example 1 does not occur, nor does the abnormal discharge shown in Comparative Examples 2 and 3 occur. In addition, Examples 1 to 1
It can be seen that the discharge time of Example 4 is almost comparable to that of Comparative Example 4, which has a mercury content of 9.0% by weight, even though the mercury content is 1.0% by weight or less.

[Effects of the Invention] As explained above, according to the present invention in which the negative electrode active material is a zinc chloride alloy powder containing a certain amount of lead, bismuth, aluminum, indium, and mercury, the mercury content is reduced. Despite this, it is possible to significantly reduce the amount of hydrogen gas generated within the battery, and there is no abnormal gas generation or abnormal discharge, and the discharge performance can be maintained at a high level, so it has great industrial value. It's large.

[Brief explanation of the drawing]

FIG. 1 shows a block diagram of an alkaline manganese battery according to the present invention. 1: Positive electrode can, 2: Positive electrode, 3: Negative electrode, 4: Separator, 5: Sealing body, 6: Negative electrode bottom plate, 7: Negative electrode current collector, 8
: Cap, 9: Heat-shrinkable resin tube, 10.11: Insulating ring, 12: Exterior can.

Claims (1)

[Claims] 1. 0.01 to 0.5% by weight of bismuth, 0.00% of lead
5-0.5% by weight, aluminum 0.001-0.0
05% by weight, indium 0.005-0.2% by weight,
A negative electrode active material for alkaline batteries comprising a zinc chloride alloy powder containing 0.001 to 1.0% by weight of mercury. 2. An alkaline battery using the zinc chloride alloy powder according to claim 1 as a negative electrode active material.